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Bolts that failed by the dozen inside four Salem Unit 2 reactor coolant pumps, idling the plant for months, were made of a metal alloy deemed unsuitable for nuclear reactors as long ago as 1984, industry and Nuclear Regulatory Commission filings show.

Manufacturer Westinghouse Electric Co. determined that parts loosened by bolt failures could have created a "substantial safety hazard" at the plant along the Delaware River had they suddenly locked up rapidly spinning parts in one or more of the 30-foot-tall coolant pumps, according to Neil Sheehan, a regional NRC spokesman.

Sheehan added that although Westinghouse considered a pump freeze-up "extremely unlikely," it considered it "prudent" to formally report the bolt issue Tuesday to the NRC and the owner of two other reactors near Newport News, Virginia, where the same bolts are still in use.

The Westinghouse notification also revealed additional details about the severity of the problem inside the Salem pumps, which circulate water from the reactor to a system that transfers heat to make nonradioactive steam for generators.

In three of the four damaged units, large metal assemblies that redirect water flows dropped from their regular positions just above water-moving impellers when retaining bolts broke or sheared off. In two of those three pumps, Westinghouse said, diffusers made contact with the impellers, which spin at thousands of rotations per minute.

"We're still reviewing how PSEG responded to the bolting issue and will be documenting any findings in an upcoming inspection report," Sheehan said. Although two of the loosened diffusers and spinning impellers made contact, "it did not cause any notable degradation" in pump flow or performance, Sheehan said.

NRC documents show that Brookhaven National Laboratory concluded in 1984 that the metals used in the type of bolts in Salem's pumps should "not be used as a reactor structural material because of its susceptibility" to damaging changes under high stress and temperature. Reactor designer Babcock & Wilcox removed the alloy from its designs the same year, and the same alloy concerns were detailed in NRC notifications to industry in 1990, 1994 and 1995.

Salem's bolt problems also prompted the NRC to notify inspectors and officials at Dominion Generation's Surry Units 1 and 2 reactors northwest of Newport News, Virginia, the only other plants to use the same "A-286" alloy bolts in coolant pumps. The Virginia company is reviewing reports from Salem "to evaluate a course of action going forward," Sheehan said.

PSEG Nuclear restarted Unit 2 over the weekend and reported the plant at 45 percent of its 1,180-megawatt capacity Tuesday morning. The 33-year-old reactor was taken offline in mid-April for a scheduled replacement of a third of its fuel, with the company reporting in mid-May that the shutdown would be extended because of the bolt problem.

Bolt failures were discovered in the same PSEG pumps during two previous refueling shutdowns for Unit 2, which take place about every 18 months. All bolts were found to be broken or sheared off during the latest outage. Some broken bolt heads were found far out of place, including at the bottom of the reactor core.

Full details on the damage and cost of the repairs and shutdown have yet to be released.

Joe Delmar, spokesman for PSEG, said that pump-maker Westinghouse issued a technical bulletin on the issue in 1996. The bulletin, he said, noted that even if all bolts on a pump failed, "it would not affect the performance of the pump and, therefore, they did not recommend going in and replacing the bolts with others with different material unless you were going into the pump for another purpose."

David Lochbaum, a nuclear engineer and director of the Nuclear Safety Program for the Union of Concerned Scientists, said Tuesday that PSEG might be found in violation of an NRC requirement that defective materials "are promptly identified and corrected."

"Clearly, PSEG violated this requirement," Lochbaum said on Tuesday, adding that the notification from Westinghouse "suggests that the defective material represented a significant condition adverse to quality."

PSEG's neighboring Salem Unit 1 and Hope Creek reactors are equipped with different types of pumps and fasteners.

Westinghouse officials could not be reached for comment Tuesday.

Salem Unit 2 is one of three reactors that PSEG operates on Artificial Island along the Delaware River southeast of Augustine Beach.